Dragonflies Wear Backpacks For Brain Study
A dragonfly snatching a meal in midair is nothing short of an aerial dogfight. First, it must predict the trajectory of its prey, maneuver a course of intersection and make split-second adaptations to outwit evasive mosquitoes or fruit flies.
All this rapid-fire multitasking takes some serious neurological circuitry — the kind scientists are so interested in, they’ve designed a tiny dragonfly backpack to measure its brain activity.
Created by Anthony Leonardo, a neuroscientist at the Howard Hughes Medical Institute (HHMI), the backpack weighs about as much as a couple grains of salt — around 40 milligrams — and compromises just 10 percent of the dragonfly’s body weight.
Neurological electric activity is captured by electrodes inserted into the dragonfly’s brain and body, on which a small computer chip amplifies and wirelessly transmits signals to a nearby computer.
Powering the computer chip without adding too much weight to the payload proved to be a difficult task. However, in collaboration with colleagues at Duke University and Intan Technologies, Leonardo came up with an ingenious solution. You know those RFID key card systems on office or apartment buildings — the ones you swipe near small pads that emit radio waves, which in turn induce a current into the card’s chip and transmit a code to unlock a door? Well, Leonardo applied similar technology. He put two long, lightweight antennae on the dragonfly backpack that pick up radio waves to power the chip.
Researchers released fruit flies inside a lab, while 18 high-speed cameras were on hand to record every second as the dragonflies took off from a perch and nabbed their prey. The backpack documented the firing of neurons, which Leonard says play a crucial roll in predators capturing their prey.
However, hunting inside a plain white lab room wasn’t so appetizing for the dragonflies. Many of the insects exhausted themselves because they where more interested in escaping than hunting. To create a more natural habitat, researchers draped the walls with imagery of a spring meadow, carpeted the floor with turf and installed a small pond.
The scenic backdrop was successful and Leonardo continued his own hunt, after the questions that fascinate him most: How neurons translate a visual scene into a plan of action, and how a dragonfly continuously updates that plan during its midair dogfight.